IT'S a killer amoeba. More than 100,000 people die each year from amoebic dysentery, mostly in developing countries where sanitation is poor. But no one knew precisely how the bug attacks the gut.

Now Katherine Ralston and William Petri of the University of Virginia, Charlottesville, have found that Entamoeba histolytica has a unique – and gruesome – strategy. It gnaws away at the gut wall, ripping chunks off living cells, chewing them up and spitting them out.

It's "purely malevolent", says Michael Blennerhassett of Queen's University in Ontario, Canada, who was not involved in the study. "This is a previously unsuspected method of attack."

Ralston and Petri labelled mouse intestines using fluorescent dyes, in order to follow their fate. Most amoebas kill cells by attaching themselves to them, but E. histolytica tears at its targets (Nature, DOI: 10.1038/nature13242). "We saw that the amoeba ingested bites of the fluorescent membranes of the intestinal cells," says Ralston. "They are impressively ravenous."

If E. histolytica is constantly grazing throughout the gut, it may be able to lurk inside a host for years without causing enough damage to lead to inflammation or disease. "The way it samples bits and pieces of the cell without ingesting it suggests this may be going on all the time, and only when a certain balance is broken does the disease set in," says Kris Chadee, a microbiologist from the University of Calgary in Alberta, Canada.

This article appeared in print under the headline "Dysentery parasites love chomping on the cells of the gut"

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